std::regex_match of the leading path may run out of stack
with long paths in debug build.
Using rfind instead to lookup the last '/' in in pathname
and skip it if found.
Fixes #4464
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Message-Id: <20190505144133.4333-1-bhalevy@scylladb.com>
(cherry picked from commit d9136f96f3)